1. Field of the Invention
The present invention relates to a semiconductor optical device.
2. Related Background Art
Light-emitting devices which emit light of multiple wavelengths are now being developed. For example, Patent Literature 1 discloses a semiconductor laser array, and the semiconductor laser array emits beams, which are different from each other, having two lasing wavelengths of 650 nm and 780 nm. The semiconductor laser array includes a GaAs substrate, a laser device portion which emits 650-nm laser light, and a laser device portion which emits 780-nm laser light. These two laser device portions are mounted on the GaAs substrate.
Patent Literature 2 discloses a multi-wavelength laser diode device that includes a plate on which at least three laser diodes having different lasing wavelengths are disposed. The three laser diodes are aligned in parallel on the surface of the plate. At least one of the three laser diodes is formed to use crystal growth on a GaN substrate, and the remaining laser diode(s) is formed on a GaAs substrate by crystal growth.
Patent Literature 3 discloses a multi-wavelength laser diode device which includes a structure in which at least three laser diodes of different lasing wavelengths are bonded onto a plate to form respective junctions. The three laser diodes are stacked on the plate. At least one of the three laser diodes is formed on a GaN substrate by crystal growth, and the remaining diode(a) is formed on a GaAs substrate by crystal growth.
Patent Literature 4 discloses a multi-wavelength laser diode device which includes three laser diodes of different lasing wavelengths bonded onto a plate to form respective junctions. The three laser diodes are aligned on a GaN substrate. At least one of the three laser diodes is formed on the GaN substrate by crystal growth, and the other laser diodes are formed on a GaAs substrate by crystal growth.
Non-Patent Publication 1 discloses a light-emitting device including three different facets formed on a GaN base and LEDs formed over these facets by crystal growth. The LEDs have different compositions of In constituent due to the different facets, and thus, their emission wavelengths are also different from each other.    Patent Literature 1: Japanese Patent Application Laid-open No. 2000-011417    Patent Literature 2: Japanese Laid-open Patent Application Publication No. 2006-135306    Patent Literature 3: Japanese Laid-open Patent Application Publication No. 2006-135323    Patent Literature 4: Japanese Laid-open Patent Application Publication No. 2008-294322    Non-Patent Literature 1: M. Funato et al., “Tailored emission color synthesis using microfacet quantum wells consisting of nitride semiconductors without phosphors,” Applied Physics Letters 88, 261920 (2006)